The overall goal of our research is to determine the role of deamidation in the lens. During the last grant cycle, we convincingly demonstrated that deamidation led to soluble aggregates, destabilized b-crystallins, altered interactions between b-subunits, and increased the a-crystallin needed to chaperone b-crystallins. These results suggest a mechanism for deamidation-induced insolubilization of crystallins and strongly support that deamidation contributes directly to cataract formation. Based on our findings, we hypothesize that deamidation decreases crystallin stability leading to aggregation that eventually triggers cataract formation. Experiments in Aim 1 will identify potentially relevant deamidations in the lens. Next, we will determine if deamidations previously identified to cause aggregation or decrease stability directly lead to cataract formation by using an in vivo model. Experiments in Aim 2 will determine the mechanism by which deamidation triggers aggregation, by identifying altered interactions within b-crystallins and with the a-chaperone. Numerous deamidation sites exist in the b-crystallins. The proposed experiments are innovative in that they will distinguish between functionally relevant sites and those that are detrimental, using state-of-the art approaches to directly test the role of deamidation in vivo. Future studies will screen for agents that prevent crystallin aggregation.